Nasty bitches are known for their extremely disgusting properties and abilities. They are the most repulsive type of women out there, usually robustly overweightalong with many other gross attributes. If I had to describe them in a word or two I'd say: Pure Filth.
Johnny: So Dillon I heard you like fucken NASTY ass bitches.
Dillon: Fucken A' my nigga, the nastier the better... they're easy game, man. In fact, I'm dating a nasty bitch named Tiffany and she's 575 lbs. of FREAK!
The definition of a girl who really just makes you feel nauseated when seeing/thinking of/hearing of. Probably ugly, probably fat, stay away from these girls as your friends will laugh about you behind your pathetically-desperate-as-shit back.
nigga #1: Dude, that girls fucking sickening, I can't believe you're dating her.
nigga #2: You're just jealous. I know you used to like her!